- You need 70 of 100 scored questions correct (70%) to pass the CO-RP exam.
- Vents and Sanitary Drainage Systems each carry 21 scored questions - the two largest domains.
- Only the 2021 IPC and 2021 IRC are testable references; Colorado amendments are not tested.
- Initial exam fee is $78; a retest costs $73 through PSI Services LLC.
Exam Format at a Glance
The Colorado Residential Plumber License Exam (CO-RP) is a computer-based, multiple-choice test administered by PSI Services LLC on behalf of the Colorado State Plumbing Board, part of the Colorado Department of Regulatory Agencies (DORA). Before you memorize a single code section, lock in the mechanics of the test itself - they shape how you should pace your review.
- 100 scored questions in 240 minutes
- Up to 10 additional unscored (pretest) questions, with 30 extra minutes added to the clock
- Passing score: 70%, meaning 70 of the 100 scored items correct
- An onscreen calculator is provided, but no formula sheets are supplied or permitted
Because unscored questions are mixed in without being labeled, you cannot skip questions based on a hunch that they "don't count." Treat every item on screen as if it affects your score. For a deeper walkthrough of how this scoring threshold is calculated, see the CO-RP Passing Score 2026 breakdown.
Domain-by-Domain Weighting Cheat Sheet
The CO-RP exam draws its 100 scored questions from eight content domains, and the official allocation is not evenly distributed. Knowing exactly where the weight sits lets you triage study time instead of spreading it thin.
| Domain | Scored Questions | Share of Exam |
|---|---|---|
| Vents | 21 | Tied largest |
| Sanitary Drainage Systems | 21 | Tied largest |
| Water Supply | 18 | Third largest |
| Fixtures and Equipment | 12 | Mid-weight |
| General Regulations | 11 | Mid-weight |
| Water Heaters | 8 | Lower-weight |
| Traps | 5 | Lower-weight |
| Residential Fire Sprinklers | 4 | Smallest |
Notice that Vents and Sanitary Drainage Systems together account for 42 of the 100 scored questions - nearly half the exam. Any candidate cutting corners here is taking on outsized risk. If you want a full content breakdown of what each domain actually tests, work through the CO-RP Exam Domains 2026 guide before your final review pass.
Vents (21 questions)
Covers vent sizing, venting methods, and how vent systems relieve pressure and prevent trap seal loss in one- to four-family dwellings.
- Distinguish between individual, common, wet, and circuit venting scenarios
- Know minimum and maximum vent pipe sizing rules from the 2021 IPC/IRC
- Understand vent termination requirements above roof lines
Sanitary Drainage Systems (21 questions)
Covers drain sizing, slope, cleanout placement, and fixture unit calculations for residential drainage.
- Practice fixture-unit load tables until sizing becomes automatic
- Know cleanout spacing and access requirements
- Understand drainage fitting and slope requirements for horizontal and vertical runs
Water Supply (18 questions)
Covers supply pipe sizing, water distribution, backflow prevention, and material selection.
- Understand demand-load calculations for residential water supply
- Know backflow prevention device requirements by fixture type
- Review approved materials and joining methods under the 2021 IPC/IRC
Key Takeaway
Study Vents and Sanitary Drainage Systems first and hardest - together they are worth more than the bottom five domains combined. Save Residential Fire Sprinklers and Traps for lighter review sessions.
Code References & Book Rules
The PSI bulletin (updated June 18, 2026) specifies that the CO-RP exam is based on the 2021 International Plumbing Code (IPC) and the 2021 International Residential Code (IRC). This is the examination-specific reference list, and it supersedes any older, more general wording elsewhere in the bulletin. A critical detail candidates frequently miss:
Additional testing-room rules to plan around:
- The test center supplies the code books - you cannot bring your own copies
- Writing, highlighting, underlining, or indexing in the supplied books is prohibited
- Personal references of any kind are not allowed
- An onscreen calculator is available, but formulas are not supplied or permitted as outside reference material
This means your tabbing and cross-referencing skills need to be built entirely in your head or through practice, since you can't rely on a pre-marked code book on exam day. Building code-navigation speed with untouched books during practice sessions is one of the highest-leverage things you can do; the CO-RP Study Guide 2026 walks through how to simulate this constraint at home.
Fees, Registration & Retest Mechanics
PSI Services LLC administers registration and testing for the Colorado State Plumbing Board. The core numbers to know:
- Initial exam fee: $78
- Retest fee: $73
For a full pricing picture, including how these fees fit into the broader cost of becoming a licensed residential plumber in Colorado, review the CO-RP Certification Cost breakdown. If you're still mapping out when to sit for the exam relative to application deadlines, the CO-RP Exam Dates 2026 guide covers scheduling windows in detail.
Eligibility & What Happens After You Pass
Passing the CO-RP exam is only one part of licensure. A passing score is followed by the DORA license application and qualification review, so your paperwork and hour verification matter just as much as your exam score.
- Residential eligibility requires 3,400 hours of practical plumbing experience
- Hours must be verified by a master plumber or registered plumbing contractor - self-verification is not accepted
- Approved education or military experience may qualify for partial hour credit
- The residential license scope covers one- through four-family dwellings, no more than two stories aboveground
- Plumbing contractor registration is a separate credential from the residential license
Candidates sometimes assume the exam is the finish line and get caught off guard by the verification process. If your hours documentation isn't already in order, start that paperwork now - it can take longer than the exam itself. Full detail on qualifying pathways is in the CO-RP Requirements 2026 guide.
Continuing Education & Renewal Cycle
Once licensed, staying active requires ongoing compliance - this is where many otherwise well-prepared plumbers slip up after the fact.
- 8 CE hours every 12 months are required for active licenses, after a first-renewal exemption for licenses issued by examination
- At least 4 code hours are required within that CE requirement
- No more than 2 safety hours may count toward the requirement per 24 months
- Licensees must attest to reading the current Colorado Plumbing Code
- CE records must be retained for six years
- State law establishes three-year plumbing license cycles beginning March 1, 2027, unless the director determines otherwise
None of this affects your exam-day performance, but it's worth knowing before you invest time studying - the credential isn't a one-time achievement, it's an ongoing compliance obligation. For context on whether the time and financial investment pays off long-term, see Is the CO-RP Certification Worth It? and the related CO-RP Salary Guide 2026.
Final-Week Rapid Review Plan
If you're within seven days of your scheduled test, don't restart your studying from scratch - triage by domain weight instead. This is the one place a structured weekly plan makes sense for CO-RP specifically.
Vents & Sanitary Drainage Systems
- Drill fixture-unit tables and vent sizing charts until recall is automatic
- Take a timed practice test section focused only on these two domains
Water Supply
- Review demand-load calculations and backflow device requirements
- Re-check approved materials list against the 2021 IPC/IRC, not Colorado amendments
Fixtures and Equipment & General Regulations
- Work through fixture clearance and installation scenarios
- Review permitting and inspection procedural questions
Water Heaters, Traps, Fire Sprinklers
- Cover the three lowest-weight domains in one focused session
- Don't over-invest time here relative to their 8/5/4 question counts
Full Simulation & Book Navigation
- Take one full 240-minute practice exam under real time constraints
- Practice locating sections in unmarked IPC/IRC copies, since the test center supplies clean books
If you're unsure how this pace compares to what other candidates report, the Difficulty Guide and CO-RP Pass Rate data both add useful context for calibrating your final-week intensity.
FAQ
There are 100 scored questions (plus up to 10 unscored) in 240 minutes, and you need 70 correct scored answers - 70% - to pass.
The 2021 International Plumbing Code (IPC) and 2021 International Residential Code (IRC), per the PSI bulletin updated June 18, 2026. Colorado's own code amendments are not tested.
No. The test center supplies the code books, and writing, highlighting, underlining, or indexing in those supplied books is prohibited. Personal references are not allowed.
Residential licensure requires 3,400 hours of practical plumbing experience verified by a master plumber or registered plumbing contractor; self-verification isn't accepted, though approved education or military experience may count toward hours.
You can retest through PSI Services LLC for a $73 fee, compared to the $78 initial exam fee. Reviewing your weakest domains - especially Vents and Sanitary Drainage Systems - before rescheduling is the most efficient path forward.